With the recent energy saving trends, attention has been paid to commonly available environmental energy that is independent of fossil fuels and the like. Power generation energy based on sunlight, wind power, or the like is widely known as environmental energy. Commonly available vibration energy may be environmental energy having no lower energy density than the above-described types of power generation energy.
Vibration power generators have been developed which generate power utilizing the vibration energy. An electret that can semipermanently retain charge is widely used for such power generators (see, for example, Non-patent Literature 1). This technique provides a power generator utilizing an electret and including a pair of opposite movable substrates that reciprocate in order to generate power, an electret on a surface of one of the substrates, and a pair of current collecting electrodes disposed on a surface of the other substrate to collect charge generated by the action of the electret. One of the pair of current collecting electrodes is grounded via a load resistor to which generated power is supplied. The other electrode is grounded without the use of a load resistor.